Process of making chemically active graphitic carbon powder



R. H. SAVAGE 2,601,953

PROCESS OF MAKING CHEMICALLY ACTIVE GRAPHITIC CARBON POWDER July 1, 1952 Original Filed Aug. 12, 1948 mzEEJznmmm 2:5 553 n d o d ananas@ w Lu awa-eval a; 14u49 Wod lrwventor: Rober-t H. Savage,

b #VIM t)His Attorvweg.

Patented July 1, 1952 t' RooEss'o-F cHEmoAn-Lriac'rv GRABHITICCARBONPOWDEB Scotia,

i 43.8541. Divided.l and this application Julieta@ One of the uses oi thisfneiii chenjiic'illy {ect-ive carbon V powder is 'fully ydescribed and laixned in 'my' copending application "Serial No. 43,855, led 'August 12, "1948; entitled "Machine A"f'guod Method for Purifying the Inert Gases, ,l1e'dfeon` currently herewith and-assigned tothesrnefassignee vas v`the "present finvention :This 'zi'pplicwtion is a division of my copending application, Serial No.43,854,`i1ed August '12,l 1948; and assigned tothe smevssigfnee :isitheA presenti-n# vention. The v'te`rin""f'graphiti carbon las -used hereinafter in the `-specieationis a'yfge'nericterm which is intended" `to mean Velemental carbon which shows anX-ray diiract-ion ptterncharacteristic of a"'grap-h'ite ltticee-nd,therefore,

also includes 'g'rphite Y vThe use of actiifgte`d"caorbnsfor the *adsorptionfifr gases vfhasb'een appreciated for' iany years.v 1 Howeveigf'the :adsorption of' such v'g'aises as'nitrogen and'h'y'drgen @by "activated carbons is accomplished' in -fany desirable' degree "only'at very low tenperture (i. vve.y 'less vthan "-jlqOY'CJ-)- Furthermore, theds'orption of vthese gases is only physical i-nnature, 'frt-he processis-revers-` ible and' merelyby'"increasing"theftemperethre of the mixture' of activated lcarbons nd fed--v sorbed gases, the adsorbedgses easily eveborete from the activated carloc'anfsY and return 'to'their free gaseous fstate.' On the' other hand'. the-adsorption rof Vsuch gases asfnitrogen and hydro# gen bychernically active grepliitifczrrbonj"powdersproduced by the comminutin'g'aiiadratus of the present inventionfisfoundtofbel-substantially irreversible and -for that y-'1"eas`oi is ireferred -to as chemical'in nature. o

lThere have also `llo'een attempts to Aprod-fcc ultrafine sized 'carbon prtic'les v1which have resulted in the production of *numerous-carbon blacks. These carbonblacksflproduced 'chiey by the' combustion.of/hydrocarbons havejinany desirable qualities l'and'hvef been'used extensively in the paint industry, rubber industry, :chemical industriesetc. VThe production rof uniformly ysized particlesv and `of ultra-tine -sized 'pa-r.-

ticles'is expensive, and theproductionof carbon t blacks has beenin '.the :past 'solely ijby. thermal means. These carbon blacks differ considerably from Athe chemically ctive igraphiticicarbons described'hereinafter.V

not intrinsic in the graphite crystalwstructure alone. ibut Ydepend uponcedsorptiori7 :such

fIhayeoundithat:if fl'eli: the :graphite seizes. lpvrhenesuhiected o '1 electronmicroscpe.- this ine idusnlireferredqto as. 1 sistsgpredomma '0.1.5' :0f il.; .ticiesfhayins funlquecheml specilcsurface of ,the gg; phiteh d -Souerermetersplner -grafxnis j `particles ,v previ. A. l, imeLhodS 'eind :in ,the .nder fofv size of :the @ery driven o. The fact that the subject graphite crystals to minute size including a continual tearing apart of the individual scales of'graphite The scissionv at right angles to the slipplan'e's. of intraplanar bonds involved is rather remarkable when it is remembered that these bonds are probably stronger than those in the diamond molecule as indicated bytheir shorter C-C distance. The Aexposed valence forces'due to the scission of these vbonds easily accounts for this activity of the graphiteparticles toward the gases mentioned at'the; relatively high room temperatures. Q

. The effect of .a non-lubricant gas vupon the wear rate of graphite .isfindicated by the following. If lthe graphite brushes bear upon a. copper disc in an evacuatedlchamber, a high friction coefficient is'measured and the brushes wear ata great'rate producing-the wear-dust. With graphite .brushes bearing on a copper disc in a chamber in which there yiswatervapor, the high frictioncoeicient (,u=80 per cent) which persists in vacuum shows an immediate drop. At a water vapor pressure of 3 mm. Hg the wear rate falls practically to Vzero l ()4` mm/'secondL and the friction b ec'ornes'low (p=l8 per cent) andconstant. This effect is foundto be quickly reversible, an equilibrium being reached between wearY rate and water vapor pressure as shown by the graph Fig. 1. At water vaporpressures above 3 mm. Hg kthebrushes can be operated indefinitely with negligible wear. When hydrogen isfsubstituted for water vapor the graphite rods'dust away at wear rates approaching those observedinpvacuum. No lubricant effect with this gas, hydrogen, .is noted even at a pressure of 600 mimi-Ig.

' Nitrogen and carbon monoxide also show no lubricant effect, at least `in the pressure range up to 600 mm. Hg, the graphite wearing in these gases as in vacuum. Oxygen shows a lubricant eiect, similar to that of water vapor but at pressures higher by a factor of about 100 (i. e. a pressure `of 200-400 mm. Hg is required to lower the wear rate to the zero range-noted with water at about 3 mm. Hg). On the other hand, the easily condensable vapors produce complete lubrication and consequently very low wear rate at pressures below mm. Hg. These vapors include ammonia, acetone, benzene, ethanol, diethylether;hexamethyldisiloxane, and n-hexane. In general the efficiency of the gas or vapor in the lubrication process seems to increase with boiling point (or ease of condensation), although there is indicated an additional specific factor relating to composition, as shown-by the difated, or filled with a non-lubricating gas. preparation of the Wear-dust is also aided by lreducing the pressure Within the chamber to a 4 ference between oxygen (B. P., 183) and nitrogen (B. P., 196).

The graphitic carbon wear-dust described and claimed hereinafter may be made, for instance, by pressing rods of graphitic carbon against a rotating metal (e. g. copper) or carbon disc in a vacuum or in the presence of a non-lubricating gas (e. g. a dry gas of the inert gas group such as argon or air free of moisture). More particularly, the production of this chemicallyactive graphitic carbon powder is .accoznpl hed bypressing the face of a 'rotating rotor'ag'ai'nst a.V graphitic carbon brush in a chamber which has been evacu- The sub-atmospheric value. Under these conditions, the graphitic carbon seizes and is rapidly disintegrated into a dust. The final comminuted product may then be collected and stored in gastight containers to keep the wear-dust fresh (chemically active); This fresh dust immediately adsorbs, apparently by chemical rather than physical'action, gases such as hydrogen, nitrogen, etc., if present. The adsorption is substantially the same whether the dust is formed in the presence of the gas it adsorbsdirectly, or whether it is formed in vacuum and they gas admitted after comminution has stopped. Furthermore, it occurs independently of the type of metal employed as the moving base, and it is observed also withgraphite rods bearing upon a graphite disc. Y.

VIn the drawing, Fig. l shows a chart o f graphite wear rate in mm3/second vs. `water vapor pressure, in mm. Hg as referred to hereinafter.

Fig. 2 is a diagrammatic illustration of the system and machine suitable for carrying out my invention.

Referring now to Fig. 2 pf the drawing, the comminuting apparatus of tligpresent invention comprises a gas-tight chamber I, within which is located a rotatably mounted comminuting wheel 2. The comminuting wheel is mounted by trunnions 8 which are supported by two bearing block standards 4. lOne of the trunnions is extended beyond its standard and is shown as shaft 5 to which is coupled one half of a inagnetic coupling B which is also contained within the gas-tight chamber I. Mounted on Wall I of chamber I are the guideand feed means for directing the graphite rod 8 against the surface of the comminuting wheel 2.V The guide means is shown as consisting of a collar 9 which is welded onto wall'I so thatthe joint will be air-tight. Collar 9 extends past wall 'I into chamber I so as to better guide the graphite rod 8 after it has been reduced in lengthduring operation of the machine. The collar 9 is threaded I0 at'its outside end to receive an end cap II and a resilient gasket I2 is provided to make the joint gas tight. Within the Acollar 9 and cooperating with the graphite rod 8 are a spring I3 and a weight I4 for exerting a constant vpressure on the graphite rod. Since wall 'I of the chamber is removable, a resilient gasket I5 is provided to make the joint gas tight.

Two baffle plates I6 are mounted in the chamber for the two-fold purpose of keeping the cornminuted material out of the trunnion bearings and for directing the falling particles in such a way that they will be collected by air-tight container I1 provided for that purpose. The base surface I8 of the gas-tightchamber is shaped so as to form a conical section I9v below the'comminuting Wheelv which serves' 'as a means loi directing the Wear-dust 2l)v intofthe removable-container I1. A pair ofy gas-tight stop-cock ltype valves 2l and 22are provided which permits continuous operation of the apparatus anda means of disattaching the container I1. Resilient-gaskets 23 are provided to make the joints,fbetween the valves 2i and 22; between valve 2| and cylindrical extension* 'Ia of the conical section I9, =and between valve 22 'and container I', gastight. l

A lsecond half 2li of the magnetic coupling is outside chamber' I and is mounted on the shaft 25 of a drive motor 2li.v Ported'tothe'chamber I by means of gas-tight tubing 2 is-agas systern which has as' elements inA the system a'vacuum pump 28 separated'rom therestof'the gas system by valve 29. An air or 'gas'inletl 'controlled by valve 3| is connected to a vdryer 32 for removing the water Vvapor from `the ventering gas. The dried gas is then compressedby pump 33 and is vstored in a pressurized "gas tank l36|. Suitable valves and 36 are provided to seal ofi each from 'the other the compressor 33 'and the tank 311., andthe tank 34 and the gas-tight chamber I. A bypass 31 is'provided from the dryer 32 to the chamber I and a valve 38 is interposed in said. by-pass T31 to -seal it 'off as the occasion demands. A purge outlet 39., ported to chamber I, and a valve 4I! for voperating said purge outlet is also provided. f

' A. number of methods of operation Willbe described. In the iirst, valves 36, 38 and '48 are closed and valve 29 is opened. 'The vacuum pump is then operated until chamber I is completely evacuated. Then valve '29 is closed'.U VThe motor 23 is then started up and the resulting rotation is transmitted to the comminuting wheel 2 via the magnetic coupling. In the presence-ofthe vacuum in chamber I, vthe graphite seizes, the `graphite crystals are ruptured producing .the

Wear-dust 20 ywhich is collected in *container- I'I.

Another method of operation .consists in closing valves 35, 38, andY 48, opening valve 2-9 and evacuating chamber I as in the .rst method. Then valve 29 is closed to seal off the vacuum pump. Valves 3| and 38 are then openedand a non-lubricating gas is permitted to enterlchamber I. The gas passes through the-dryer and then the dry gas is bled into chamber -I by -valve 33 until some desired pressure is attained. The comminution process is carried onas described in the first method.

Another method is very similar to thesecond one described except that the Vgas is vdriedand then compressed by pump 33' and is held in pressurized tank 34 'with valve 36 closed. A fter chamber I is evacuated and valve 29 is 'shut,'va1ve 36 is opened and the dry non-'lubricatin'ggas is permitted to enter the chamber until Asome desired pressure is reached.

Another method of introducing non-lubricating gas into the gas-tight chamber consists of purging chamber I with a non-lubricating gas. This consists of compressing dry non-lubricating gas into tank '34 and then `opening lonly valves 3S and 4G. The gas under pressure'enters chamber l 'and forces the gases that 'are in there'at thai-l time out of the chamber through purging outlet 3S. Then valves-36 and 40 are both closed, the gas remaining in the chamber being nonlubricating in nature. Then, the comm'inution process. is begun and carried on in-the manner as previouslydescribed.

V.When it is necessary "toreplenish-the 'supply 6 of gr aphit'e.l cap'` fI2 l is f-takenf o land-Weight yI4 and spring I3 arelif'emvedfThen-fa new stick lof graphite` is insertedinfwcollan and allrthe parts are reassembled: --Infco1lectingthe weardust, afterfthe container YI-I lis ffilled, both -valves 2l and'22 are closed-and lthen by detaching'valve 22 from valve 2I,` the *container Hand valve 22 can befremoved as ya-unit without exposing the Weardust to any-contaminantsjand lWithout losing '-the non-lubricant gas Whichiills chamber I.

. Then another collecting container and-valvecan be attached and the valves reopened to lproceed with the process 'as before t Y It should `be `obviousftl'ratjcertainmodifications and improvements vcanbe `readily made, lsuchv as (l) using'eitherof theftwo'fparallelfaces 4ofthe comminuting v'vheel as the ccnamin'uting surface instead of the cylindrical face; Y(2) including the drive motor withinthe v'gas-*tight chamber so `as to do away with fthe vvclutching arrangementand (3) using an appendix vchilled by'acold bodysuch as liquid nitrogen 'and 'projecting into the Ycomminution chamber for'the lpurpose of condensing any Water 'vaporpr'e'sent v'to 'insure 'dryness Within the comminution chamber. 'It should also be obvious that whenl a magnetic clutch'isl used, vthe Wallbetvveen the ,two .parts ofthe clutch should be non-magnetic.

In View of theuni'queness of the'claimedprod- -uct and the necessity oi'distingui'shing it from other 'carbon'productsit has been deemed .advisable to describe this chemically 'active graphitic carbon interms of its'dim'ens'ions and physical properties, aswell as 'its chemical properties and activity. The general physical appearance of the wear-dust is that in an' agglomerated mass it is of a non-flocculentgranular'nature. n

As pointed out vhere'in'ibove kthe"ccniminuted *productl has an'unu'sualainityfor' diatomic or polyatomic gases and will''irre'vers'ibly adsorb a gas such as hydrogenat'V roon'itemperature and at 10W pressure, a phenomenon notshov/nby activated charcoal. `It is 4Wellknown that .certain activatedcharcoa'ls and other activated Aforms of carbon will adsorb manylfgases .atflow temperatures but upon gentle heating to room .tempera-V tures these .gases .(ez'cepting' the oxides) are driven oi. Thus,v this type of adsorption is reversible. On the other hand it `has`been .'found that the graphite Wear-dust:describedherein adsorbsgases such as hydrogen, nitrogen, methane, carbon monoxide, and 'carbon' dioxide, not only at low temperatures but also atroom temperature, andfurthermore-only those which are adsorbed only at low Ytemperatures can later be recovered at` higher temperatures.- This is due .to the fact that the adsorption characteristic of my new product is permanent and irreversible. v'Because'of thefirreversibleinature of the reaction, it is 'believed-.that thegadsorptmn may be chemical in nature. .'Onthe-otherhandythe Wear-.dust does not adsorbthe inert agaseous elements, e. g., neon, helium, argon, etc.,lat room temperature. Y The adsorptionfof hydrogen by fresh graphite weardust,at room temperature,V is Kinterpreted as a chemical adsorption *satisfying theopen valencebonds resulting 'from the openngfo'f the graphite lattice during the-process Jof lfrictional seizure. Ithas been determinedthat the amount of hydrogen adsorbed by the dust is about 100,000 times greater than that adsorbed by'a'typical activated charcoal at-the1sametemperature and pressure. This irreversible or chemical adsorptiem-when measredkatroom temperature, represents a chemically-active surface ofthe order of five square meters per gram.

The chemical adsorption discussed above should be diiferentiated from the physical adsorption of the graphitic carbon wear-dust. The wear-dust is capable `of physically or reversibly adsorbing gases at low temperatures. Thus, the reversible or physical adsorption, of the claimed graphitic wear-dust, as measured at low temperatures (-196 C.) indicates a-total physical surface area of the order of 435, square meters per gram. ,A Y- A From these data and also from the confirmatory results ofelectron microscope studies, it has been found that the process of wear results in a fine sub-division of `the individual graphite particles, increasing the total surface by several hundred fold to within the range of the nest colloidal carbon blacks (color blacks), but without producing the contaminated surfaces which characterize the colloidal carbon blacks, and which distinguish them from elementary carbon.

Measurements on representative wear-dust samples have indicated that the total surface may be as high as 435 m.2/g. which is many times greater than the total surface of ordinary graphite powder (which is employed to make carbon brushes) which is of the order of 3 to 10 m.2/g. The total surface of typical rods from which the wear-dust may be made is of the order of 1 to 2 m.2/g., and therefore the total surface of the wear-dust is approximately 99.5 to 99.9 per cent fresh surface developed in the wearing process. The results of chemical adsorption tests have shown that the chemical type hydrogen adsorption was approximately 2 cc./g. V(std. temp. and press.) and chemical type nitrogen adsorption was approximately 0.2 cc./g. (std. temp. and press). Thus, only a portion of the fresh surface is chemically active, but this activity is unique in the phenomena, of adsorption `by carbons. 1 l I,

The 2 cc./g. hydrogen adsorption, determined experimentally, although many times larger than that reported f or anyprevious carbon,V is only 2% of the physical monolayer nitrogen adsorption of 100 cc./ g. determined at low temperatures (about 196 C.). The hydrogen adsorption would seem to represent the proportion of carbon atoms which'have been exposed so as to show one or more strong valences of unsaturation, such as those of free radicals. This exposure would not occur if the graphite crystal is simply delaminated or scaled away, but would occur if the crystal is opened both along the main cleavage plane and at right angles to this plane (so as to uncover both face atoms'and edge atoms). e Y

The laminar structure of graphite. together' with the indication that the chemically active surface represents only a small proportion of the total surface, suggests that the wear-dust particles are composed of thin plates, and that only edge atoms combine .with hydrogen while face atoms in the main cleavage plane of graphite make up most of the total surface area. In this case the area of the chemically active surface and the fraction of the surface atoms which are chemically active may be readily calculated from the lattice dimensions. The main cleavage plane of graphite consists of carbon hexagons with the smallest interatomic distance 1.42 and the separation between planes 3.39 The area per carbon atom along an edge perpendicular to themain plane isithereforer l.42 3.39=4.81 sq.

If the hydrogen adsorption isv due to one-to-one combination of hydrogen atom with edge carbon atoms, the chemically active surface covered by 1.98 cc. per gram is found to be about 5.12 m.2/g. Any other lattice points reacting with hydrogen would lead to an even smaller value for the area of the chemically active surface. The results oli some experiments indicated a total surface area of 435 mE/g. Since the chemically active surface was determined to be about 5 m.2/g., the remaining total surface, 430 m.2/g., is considered to represent facial area. Although the chemical surface represents only a small fraction of the total surface, its absolute magnitude, 5.12 m.2/g., is large compared with the total surface of the rod from which the dust was worn and is comparable with the total surface of natural graphite powders.

In order to determine the value of the equivalent particle size it may be assumed that the particle size represents the diameter of hypothetical spheres (or the edge of cubes), calculated from the equation da=6pS where da is in microns when S is in m.2/g. and the density p is in g./cc. (2.25 for graphite). It is convenient to use the spherical model for comparison with the more usual forms of black carbon but a laminar model with a large ratio of area to thickness appears much more likely from the evidence. For a plate-like particle of area A and thickness t, the surface area may be considered as 2A with only a small error if the ratio of edge surface to total surface is small. The mass of the particle is At p, and the surface area per unit mass S=2/tp. As long as the thickness t remains small compared with the area A, the specific surface area of the graphite is independent of the size and shape of the particle and is determined by the thickness. For weardus't with ASr=le35 101 om. z/g., therefore, the indicated thickness t=20.4 108 cm.

From the specific surface alone there is no limitation on the'size and shape of plate-like particles; only the thickness is determined. A probable limitation on the face to edge surface appears in the ratio of total surface (as determined by nitrogen adsorption at 195 C.), to chemical surface (as determined by hydrogen adsorption at room temperature). The ratio of total surface atoms to hydrogen atoms adsorbed chemically has been calculated to be :1. If this is assumed toY represent the ratio of face atoms to edge-atoms, the average size of the plate-like particles of the graphite wear-dust may be calculated. Calculations show that circular plates ofaverage radius 1720 and thickness 20.4 satisfy the requirements for both total and chemical surface, assuming combination of hydrogen with edge atoms.

Adsorption methods have provided one of the best means for determining specific surface and, by calculation, the particle diameter of fine pigments.

Of particular interest is the low temperature nitrogen adsorption method. The specific surface area andfparticle diameter of the graphitic carbon wear-dust was measured by this method, and in the following table, is compared to the specic surface area and particlev diameter of representative carbon blacks. The tables below containing the representative values were taken from the book Surface Area of Colloidal Carbons, vol. 3, pp. 22-23, Columbian Carbon Co. (Binnie and Smith, distributors), printed by Mack Printing Co., Easton, Pa., copyright 1942.

TABLEif Particle size amtsm'facey area hyd.; nitrogen adsorption (Emmett et al.)V

Diameter (11m)y v Area Carbon (SqlnL/g.)

Thermatonic Acetylene Graphite Wear Dust TABLE 2 Particle size and surface area by nitrogen adsorption (Smith et al.)

Diameter (Calculated) Surface Area Carbon (sqm/g.)

NONIMPIN GEMENT BLACKS P-33 Lampblack Gastex 15- 28 40 Acetylene; 64

IMPINGEMENT BLACKS Graphitized Black Grade 3 Rubber CK-S E. Ink Black M. Ink Black o'. r.' color Back Graphite Wear Dust It can readily be seen that the graphite wear dust has a much greater area and smaller size than those of the carbons listed above and examined by Emmett et al., 'and similar results as to all but one carbon is shown when comparing Smith et al. results. It should be remembered that the impingement blacks are produced by combustion process and the products do not have any special chemical activity or affinity. As far as is known, the claimed graphite wear-dust is the smallest size carbon produced by mechanical means, and it has chemical properties which are not found in any of the thermally produced carbon blacks.

Preliminary studies of irreversible nitrogen adsorption by the graphite wear-dust indicate results that are considerably less than that for hydrogen. On two tests, the nitrogen adsorption has been found to be 0.13 cc./g. (STP) or higher. The fact that it is so large is rather remarkable since molecular nitrogen does not react chemically with activated charcoal as pointed out by R. B. Anderson and P. H. Emmett, J. Phys. Colloid Chem., 51, 1327 (1947). Preliminary adsorption data for methane showed an adsorption of about one-half that obtained with hydrogen; that is, approximately the same number of hydrogen atoms were involved per gram of graphitic Wear-dust for these two gases. The carbon monoxide adsorption is indicatedto be ofthe same order as for hydrogen,

'ment groupby fcleaningfrupfgthe traces of nitro;-

gen and hydrogen which at present areso difficultf= to remove; f-This use is described and claimed in my copending application Serial No. 43,855, filed eAugust 12,v 41948;,.referred to above.

Another use is Vas. a getter in,,vacuumtubes. y A

getter is' a material that 'wiugpeimanenuy'Tremove undesirable gases from af va'cuum 'device 'by combining with the'undesirable gases such as carbonf monoxide carbon dioxide, nitrogen, hy-' drogengoxygen,etc., i'

It is true that the product of the present invention is primarily elemental from a chemical viewpoint. It is also truc, however, that it constitutes a new and useful product which is distinguished clearly by its physical'properties and its chemical characteristics from all generally similar products. Thus, while several representative uses of the product are described above, it will be understood that the uses are not to be limited to those described above, as further uses will suggest themselves to those skilled in the art.

While I have shown a particular embodiment of my invention, it will be understood, of course, that I do not wish to be limited thereto since many modifications may be made, and I therefore contemplate by the appended claims to cover any modications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A method for producing chemically active ultra-fine sized graphite particles comprising the steps of evacuating the space enclosed by the air tight housing in which the comminution process takes place, and then comminuting the graphite within said evacuated housing by pressing it against a moving surface.

2. A method for producing chemically active ultra-iine sized graphite particles comprising the steps of evacuating the space enclosed by the air tight housing in which the comminution process takes place, then filling the gas-tight housing with gas chosen from the gases of the inert gas chemical group, and then comminuting the graphite within said housing in the presence of said gas by holding said graphite against a rotating surface.

3. A method for producing chemically active ultra-Ene sized graphite particles comprising the steps of purging the gas-tight housing in which the comminution process takes place with substantially dry sub-atmospheric pressure air having a partial water vapor pressure of less than 1 mm. Hg, then sealing said housing and then comminuting the graphite within the space enclosed by said housing in the presence of said dry air said comminuting being carried out by holding thkemgraphite against a rotating surface.

Ti. )'method for producing chemically active ultra-fine graphite particles comprising the steps of evacuating a space enclosed by an air-tight housing, lling said space with a gas chosen from the group consisting of dry air, nitrogen, hydrogen, carbon monoxide, argon, neon, and helium and comminuting a graphite body within said gas-filled space by wear against a moving surface.

5. A method for producing chemically active ultra-iine sized graphite particles comprising the steps of evaouating the space enclosed by the airtight housing in which the comminution processY 11 takes place. then filling the; gas-tight housing with dry nitrogen gas, and comminutng the graphite within said housing in the presence of said gas by holding said graphite against a rotating surface.

ROBERT H. SAVAGE.

REFERENCES CITED The following references are of record in the Toumin Mar. 18, 1879 Number Name Date' f Mertes' Oct. 18, 1898 Hazelton Feb-17, 1903 Frank May 4, 1909 Hamilton July 26, 1921 Plauson Mar. 9, 1926 YKramer Feb. 17, 1931 Tone Feb.V 26, 1935 Rogers Nov. 24, 1936 Lund Aug. 27, 1940 Sheldon Apr. 6, 1943 Anderson Aug. 31, 1948 

1. A METHOD FOR PRODUCING CHEMICALLY ACTIVE ULTRA-FINE SIZED GRAPHITE PARTICLES COMPRISING THE STEPS OF EVACUATING THE SPACE ENCLOSED BY THE AIR TIGHT HOUSING IN WHICH THE COMMINUTION PROCESS TAKES PLACE, AND THEN COMMINUTING THE GRAPHITE 